Searching for a motor

[S6PNJ]

Asking the hive mind...

I need a small dc motor, dimensions are:

Dia 17.5mm (could be slightly smaller and I'll make a sleeve, but not larger)
Body length - 37.25mm (not too critical , could be +- 5mm possibly, could actually be much shorter and I'd just make a packing piece to make it the right length)
Shaft diameter - 4mm (could go up to 5mm possibly, if smaller I could make an adaptor possibly)
Shaft length - 28.75 (not too critical - can be longer but only up to 5mm shorter)
Voltage 7.2VDC (I think - need to check to confirm but pretty sure it would be this as battery supply to unit the motor sits in is 7.2VDC)

It's fairly low torque, only runs a small 6 bladed fan to 'swirl' air around.

Any thoughts?

Edited by S6PNJ on Saturday 4th February 16:53

[GliderRider]

You could look at model railway motors and radio control servo motors. The former are probably more suitable for continuous running. Neither will meet your shaft diameter/length requirement. A 4mm shaft is mighty big for a 17.5mm dia motor. You can add a 4mm dia shaft extension, but you may need to make sure it and the fan are well balanced to prevent whipping and fatigue on the motor shaft.

This document describes the pros & cons of various model railway motors. Motors for Railway models
This Minebeamotor should work if you fan doesn't overload it: Minebea PPN7PA09C2

If that one isn't suitable, the same seller has a large range of other motors.

This square motor may fit, altough they say its is designed for a minimum of 9V: Square motor

Edited by GliderRider on Saturday 4th February 17:52

Edited by GliderRider on Saturday 4th February 17:56

[S6PNJ]

Thanks, much appreciated.

Sadly the linked one (second link) is 19.4mm across corners, so too large - the 'hole' mine fits in is 17.5mm max.

The 'fan' it powers doesn't run continuously, runs for about 5 seconds then stops until commanded again.

It's definitely a 4mm shaft as the fan blade is held in place with 2 M4 nuts, one either side. Click for bigger pic.

[GliderRider]

That shaft looks like its a tube or blind-drilled rod that's been pushed on the motor shaft with an interference fit. If you can get it off, you should be able to re use it on the next motor.

Here's another motor: Minebea SS10J

[S6PNJ]

Cheers again - yes, I've just checked - it is a tube so I guess it will come off (maybe with a bit of heat via heat gun) if I can find something suitable to put it back onto. I guess that certainly helps.

Without accurately measuring it, I'd guess at 1-1.5mm - I have various precision drills I can check the dia of the hole with (but not this evening!)

Hmm - I wonder - https://www.aliexpress.com/item/1005001414029131.h... might be a possibility

Getting closer - https://www.aliexpress.com/item/1005004138434436.h...

Edited by S6PNJ on Saturday 4th February 18:21

[GliderRider]

it looks like you are getting very close now.

Here's another. 17mm dia. but only a very short shaft to push your extension on:

Mabuch RF-130CH

[S6PNJ]

Fab! Will have to have a tug at my shaft tomorrow (oo er missus) and see how much length I have.

[GliderRider]

S6PNJ said:

Fab! Will have to have a tug at my shaft tomorrow (oo er missus) and see how much length I have.